1. Field of the Invention
The present invention relates to a digital broadcasting system. More particularly, the present invention relates to an apparatus and method of managing a reception state of data in a digital broadcasting system, in which a set-top box in the digital broadcasting system monitors states of a cable network, a broadcasting channel and received data and, in the mean time, when an abnormal state or an error of the received data is generated, transmits a notification message depending on the error to a head end.
2. Description of the Related Art
Such a digital broadcasting system has been used for digital terrestrial broadcasting, digital satellite broadcasting, cable digital broadcasting, etc. according to transmission media of broadcasting data.
These digital broadcasting services compress program information of each channel in conformance to MPEG (Moving Picture Experts Group) coding standards, and multiplex and transmit programs corresponding to a plurality of channels on the basis of a digital modulation scheme of each transmission medium. Thus, digital broadcasting data can transmit program information through tens to hundreds of channels without using many repeaters, like analog broadcasting signals.
In general, the digital broadcasting system for promoting the cable digital broadcasting services is composed of a head end for transmitting digital broadcasting data related to broadcasting and for processing data uploaded from a subscriber, and a set-top box, as a digital broadcasting receiver, for converting the digital broadcasting data transmitted from the head end into broadcasting signals, for restoring the converted signals to original video and audio signals and for providing the restored signals to a digital television (TV).
The head end refers to a main control center equipped with technical installations capable of receiving, preparing and re-transmitting the program information in the digital broadcasting system. The set-top box refers to a home communication terminal for providing bidirectional multimedia communication services to the subscriber like video on demand (VOD) services.
For the cable digital broadcasting system, compression technology of audio and video data employs a MPEG-2 (Moving Picture Experts Group-2) protocol, and amplitudes and phases of signals are modulated according to a QAM (Quadrature Amplitude Modulation) scheme as one of digital modulation schemes.
The set-top box, a digital broadcasting receiver, in the digital broadcasting system is mainly directed to decoding of digitalized broadcasting data, management data and control data transmitted from the head end and provision the analyzed result to the digital TV.
Specifically, the set-top box receives/manages each of the data transmitted from a digital broadcasting server or an audio/video server, a service information server and conditional access server which constitutes the head end, wherein the service information server transmits broadcasting channel information and the conditional access server provides information on the subscriber and key information capable of decoding encoded broadcasting data. In the meantime, the set-top box converts the broadcasting data into broadcasting signals according to a request of the subscriber, and provides the converted signals to the digital TV.
FIG. 1 is an entire block diagram for explaining network connection of a general digital broadcasting system.
Referring to FIG. 1, the digital broadcasting system includes ahead end 10, a CMTS (Cable Modem Termination System) 30, a set-top box or a digital broadcasting receiver 20, and a digital TV 40. The head end 10 includes a service information server 11, a conditional access server 12 and a digital broadcasting server 13.
The set-top box 20 includes a cable modem 21, a data processor 22, and a conditional access processor 23.
The service information server 11 of the head end 10 provides service information for providing digital broadcasting services.
These service data provided at the service information server 11 may include program information such as program identifier (PID) and event information which are provided at the digital broadcasting server 13.
Further, the service information server 11 transmits the service data to the CMTS 30 on the basis of an Internet protocol (IP) network.
The digital broadcasting server 13 provides broadcasting data in which video and audio data of programs received or prepared at the head end 10 are included.
At this time, the digital broadcasting server 13 can compress the broadcasting data in conformance to MPEG coding standards, encipher the broadcasting data for preventing malicious application, and transmit the enciphered broadcasting data.
The digital broadcasting server 13 transmits the broadcasting data to the set-top box 20 through the broadcasting channels of the cable network.
The conditional access server 12 manages various information, such as key information capable of decoding the enciphered broadcasting data, information on authority of a subscriber to watch each program, purchase history information on the subscriber, etc., and simultaneously provides the conditional access data, in which the key information and the authority information are included, to the set-top box.
In this case, the conditional access server 12 can transmit the conditional access data to the set-top box 20 through the CMTS 30 either in an EMM (Entitle Management Message) form or in an ECM (Entitle Control Message) form.
The CMTS 30 converts data of IP packet format, which are received from the service information server 11 and the conditional access server 12 through the IP network, into cable data for transmitting the data of IP packet format to the set-top box 20.
The set-top box 20 converts broadcasting data into broadcasting signals and transmits the converted signals to the digital TV 40, wherein the broadcasting data are received through the corresponding broadcasting channels depending on channel selection of the subscriber.
Specifically, the cable modem 21 of the set-top box 20 receives the service data which are converted into the cable data at the CMTS 30, transmits the received data to the conditional access processor 23, and transmits the broadcasting data to the data processor 22.
The conditional access processor 23 manages the key information and the program-specific watching authority information of the subscriber based on the conditional access data provided from the conditional access server 12. In the meantime, when the subscriber selects a channel, the conditional access processor 23 checks whether the subscriber has authority to watch the selected channel or not. When the subscriber has the watching authority, the conditional access processor 23 decodes the encoded broadcasting databased on the key information.
The data processor 22 decompresses the broadcasting data which are compressed according to the MPEG coding scheme, and converts the decompressed data into the broadcasting signals. Then, the data processor 22 transmits the broadcasting signals to the digital TV 40 in order to provide the digital broadcasting services to the subscriber.
This method of providing the digital broadcasting services of the digital broadcasting system will be described in brief.
The service information server 11 transmits service data, in which program information and event information are included, to the set-top box 20. The conditional access server 12 transmits both key information and watching authority information of the subscriber to the set-top box 20.
The digital broadcasting server 13 transmits broadcasting data, in which audio data and video data are included, to the set-top box 20.
When a subscriber selects the program information, the set-top box 20 obtains channel information of the selected program information, and checks whether the subscriber has authority to watch the selected program information or not.
Meanwhile, when the subscriber has the authority to watch the selected program information, the set-top box 20 detects frequency information to receive the broadcasting data according to the obtained channel information, and then receives the broadcasting data through the detected frequency information.
The set-top box 20 decodes the received broadcasting data using the key information, decompresses the decoded data according to the MPEG coding scheme, and then converts the decompressed data into broadcasting signals.
Then, the set-top box 20 transmits the converted broadcasting signals to the digital TV 40.
However, the general digital broadcasting system takes a manually operated system where the set-top box 20, as the digital broadcasting receiver, processes the broadcasting data provided at the digital broadcasting server 13 into the broadcasting signals and transmits the processed signals to the digital TV 40.
Therefore, for the digital broadcasting system, when an error is generated either from any one of the servers 11, 12 and 13 of the head end 10 or from any one of the cable network and the broadcasting channel, the set-top box 20 fails to receive any one of the broadcasting data, the service data and the conditional access data. For this reason, the digital broadcasting system is confronted with a broadcasting mishap that cannot provide the digital broadcasting services to the subscriber.